After reading the datasheet (rev. C) and reading some (all?) discussions here about running the ATmega328PB from a crystal oscillator i'm still somewhat confused ...
Here is what is think to understand so far:
- it does not have the full swing oscillator option
- low power oscillator option can only be used up to 16Mhz
- people where reporting problems running them from 16Mhz oscillators but that was for early engineering samples (?)
What is still not clear to me is this:
- do current production chips have problems running from an 16Mhz crystal oscillator?
- how critical is the choice of the oscillator and the bypassing caps?
- are the capacity values (12-22pF) in the datasheet valid for production chips?
- what about rel. long traces on a prototype, like having the AVR on a throughhole adapter and the oscillator also an a mini board (for fast exchange), so we are talking about ~20 mm traces?
i use this somewhat heavy-handed setup in prototype boards for years now and have never had problems running various ATmegas with it ...
- what about running it from an external clock? is up to 20MHz within spec?
according to "12.7. External Clock" no, 16Mhz top!?
according to various other places in the datasheet, especially "34.4.3. External Clock Drive" and "34.3. Speed Grades" probably yes ...
If the ATmega328PB would not be so tempting for my project due to the many timers it has i think i would not even bother ...